[9] PAGE 15. _Pleurobrachia rhodactyla_, Agassiz. This is one of the numerous free-swimming marine animals, belonging to the _Ctenophores_. A group of the sea-jellies which have the pretty rows of paddles adown their long diameter. They are usually about a pigeon’s-egg in size, are oval, and in their element almost invisible, so colorless and transparent are they. A close inspection shows the paddles to be iridescent. [10] PAGE 15. _Idya roseola_, Agassiz. Another form found near the shores of Nahant. [11] PAGE 16. The _Physophoridæ_ include the interesting forms, _Physalia_ (Portuguese Man-of-War), _Porpita_, _Vellela_, etc. The first named indicates the character of the group, as its fleshy mass is surmounted by a beautiful bladder-like float, a mere bubble of membrane. These forms are not often seen out of tropical waters. [12] PAGE 16. The term zooids is applied to the mass of tentacles and other fleshy parts of the _Physophoræ_. The long, extensile feelers are for prehension; others aid in locomotion, and some are reproductive; others are feeders for the entire colony. Thus it will be seen that these creatures are in a sense compound animals. [13] PAGE 24. Alcyonarian corals from an order in the class _Actinozoa_. [14] PAGE 24. Professor Moseley, of the “Challenger” expedition, was enabled to examine the light from these beautiful forms by the aid of the spectroscope, and found that it consisted of red, yellow, and green rays only. [15] PAGE 25. _Acanella normani Verril._ A pretty soft coral, which has been dredged off the New-England coast by the fish-commission. This is a revelation to science, as no one was ready to believe that such forms, so common to the tropical regions, would be found where they were. The Gulf Stream runs so close to the North-eastern States, it will not, on reflection, seem strange that some creatures common to the warmer waters may find a home there. [16] PAGE 25. _Primnoa resida._ [17] PAGE 25. _Paragorgia arborea._ [18] PAGE 26. _Pennatulidæ._ The name of a family of marine animals, which includes the _Umbellularias_, _Veretillum_, etc.,--the last highly phosphorescent.